On the Holder Continuity of Multiple Valued Harmonic Functions Luis Caffarelli Indiana University Mathematics Journal 1976 text pdf 10.1512/iumj.1976.25.25007 10.1512/iumj.1976.25.25007 en Indiana Univ. Math. J. 25 (1976) 79 - 84 state-of-the-art mathematics http://iumj.org/access/